Relational database systems store tables of data which are typically linked together by relationships that simplify the storage of data and make queries of the data more efficient. Structured Query Language (SQL) is a standardized language for creating and operating on relational databases.
One operation in SQL is the query, which retrieves data from a table or an expression. Some query statements have no persistent effects on a queried database. However, some queries can have persistent effects. Moreover, some queries can retrieve so many different records in a database that the query is executed on the database for an excessive amount of time and/or utilizes an unreasonably large amount of computer processing resources. Such a query can be referred to as a runaway query.